1. Field
The following description relates to a semiconductor device and a manufacturing method thereof. A semiconductor device may be configured to reduce a doping concentration at an active region and enhance a breakdown voltage by performing counter doping to a region where a Schottky barrier diode is formed.
2. Description of Related Art
In order to increase a switching speed of a semiconductor electricity device and to reduce a power consumption, reduction of an on-resistance and a gate capacitance is preferred. For the reduction, a method of incorporating a Schottky Barrier Diode (SBD) into the semiconductor electricity device, such as a metal-oxide semiconductor field effect transistor (MOSFET) has typically been applied.
A Schottky Barrier Diode (SBD) forms the Schottky Barrier by means of a junction between metal and semiconductor. That is, such metal-semiconductor junction is formed between a metal and a semiconductor, creating a Schottky barrier. Typical metals used are molybdenum, platinum, chromium or tungsten, and certain silicides, e.g. palladium silicide and platinum silicide; and the semiconductor would typically be n-type silicon. The metal side acts as the anode and the n-type semiconductor acts as the cathode of the diode. This Schottky barrier results in both very fast switching and low forward voltage drop.
With regards to a MOSFET embedded with an SBD which uses drift current of various carriers, a time delay by charge accumulation due to an injection of a few carriers is not generated, thus, a fast switching may become possible. Also, efficiencies are improved as switching frequency increases.
However, the SBD has disadvantages in that a maximum reverse voltage is low and a reverse direction leakage current is heavy. Also, with regards to a semiconductor device embedded with the SBD, a Breakdown voltage (BV) of the Schottky barrier diode is determined according to a Barrier Metal and an EPI Resistivity. Therefore, if a high concentration Epitaxial layer having a low resistivity is used in a semiconductor device in which the SBD is embedded, an on-Resistance (RDS(ON)) may be disrupted due to the increase of the resistance in the MOSFET drift region.
FIG. 1 is a diagram illustrating an example of a graph of a breakdown voltage change value, according to an EPI Resistivity of a semiconductor device embedded with a usual MOSFET (B) and a conventional Schottky barrier diode (A). As illustrated in FIG. 1, it should be appreciated that a breakdown voltage value is lower than the MOSFET (B) for an identical value of the EPI Resistivity.
Conventionally, to solve this problem, minimization of an electric field was attempted by applying a Guard Ring or a trench field plate. However, this method has a limitation because the distribution characteristic of the electric field on the substrate surface of the semiconductor device is largely different from the theoretically targeted range.